The present invention relates generally to a spray system for a dishwashing machine, and more particularly, to such a system that includes a spray manifold that can be easily removed for cleaning and then easily replaced.
Dishwashing machines fall into two generally distinct but somewhat overlapping categories, namely, domestic or home machines, and commercial machines such as are used in restaurants, institutions or other public facilities. This latter category is itself divisible into various types of commercial machines.
Two of the most common types of commercial machines are the single rack-type and the conveyor-type. The former includes a single chamber into which a rack of soiled ware can be placed. Within the chamber, the entire cleaning process including washing, rinsing and drying is performed on the rack. Multiple racks must be washed sequentially, with each rack being completely cleaned before the next can be operated upon.
Conveyor-type machines, on the other hand, include a conveyor for carrying racks of ware through multiple stations within the machine. A different operation is carried out at each station, such as washing, rinsing, or drying. Thus, multiple racks of ware can be placed on the conveyor and moved continuously through the machine so that, for example, while one rack is being rinsed, a succeeding rack can be dried.
Examples of both of these types of commercial dishwashing machines can be found in U.S. Pat. No. 4,439,242, issued Mar. 27, 1984 to Hadden.
Of course, any dishwasher must thoroughly clean and sanitize the ware upon which it operates. To this end, an organization called the National Sanitation Foundation (NSF) was formed in the late 1940's. One of its functions is to provide minimum standards for commecial dishwashing machines to assure that ware has been adequately cleansed and sanitized.
While NSF standards are theoretically voluntary, public health and sanitation officials in the United States are believed to rely heavily upon them. A manufacturer is permitted to place an NSF label on the equipment to show that its design, manufacture and operation meet all of the minimum NSF standards for that particular type of equipment. Many sanitation officials will not permit installation or use of commercial dishwashing machines within their jurisdiction unless the machines have NSF labels, indicating that they are "listed" as being recognized by NSF. In effect, NSF standards are so well accepted that very few commercial dishwashing machines are sold in the United States without NSF listing.
A typical dishwashwer operates to clean ware by directing pressurized streams of heated water against the ware. Thus, a pumping system is generally provided that directs the water into a spray system having a plurality of nozzles for forming the pressurized streams. The particular construction of the spray system is dependent upon the type of machine, and in the case of a conveyor-type commercial machine, the spray system is disposed above and below the conveyor path. In a typical configuration, one or more fluid conduits extend from a spray manifold across the path in a generally transverse orientation above or below the conveyor. More than one such manifold is usually provided, with various ones thereof dedicated to washing, rinsing, or the like.
Since most dishwashers recycle water through the spray system (other than rinse water, which is fresh), wash water that has previously been in contact with soiled ware is circulated through the spray system. Although larger soil is typically screened or filtered, some smaller soil particles and other debris can pass through the system, and present at least the potential for accumulation within the spray manifold. This not only represents an unsanitary condition, but can cause plugging of spray nozzles or interference with the water flow, thereby reducing the pressure or amount of water reaching the ware.
This problem has been recognized by, among others, the NSF. In its Standard No. 3 for Commercial Spray-Type Dishwashing Machines, NSF has provided in Section 4.12 as follows:
"Spray Arms: Spray arms or similar devices shall be readily removable and easily cleanable, or easily cleanable in place . . . Spray arms or similar devices shall be designed and constructed to assure their reassembly in proper alignment."
Dishwasher manufacturers have followed this standard in designing and constructing conveyor-type machines. Moreover, many local health regulations specifically require the cleaning of spray arms at predetermined periodic intervals.
Despite the need to remove the spray manifolds for cleaning with relative frequency, such removal and the subsequent reinstallation has been a relatively tedious process. Typically, doorways are provided along the forward side of a conveyor-type machine to give access to the wash and rinse chamber interiors. However, to give such access to the chambers and to other components such as drains, screens and the like, the water supply conduits to the spray manifolds should preferably be placed at the back side of the machine. Accordingly, the connection of a manifold to its supply conduit must also be placed at the back of the machine, where it is almost impossible for the machine operator to reach the typical type of quick-connect/disconnect attachment means. Thus, if the supply is located remote from operator accessability, it is necessary to provide a coupling and uncoupling system which can be operated from a remote position without the use of tools.
One possible solution to this problem is proposed in U.S. Pat. No. 4,257,559, issued Mar. 24, 1981 to Noren. A spray manifold is provided that consists of a single cylindrical tube having a plurality of spray nozzles formed along the tube. At the rear side of the machine, a conical outlet is connected to the water supply conduit, so that the cylindrical manifold is placed over the conical outlet to form a fluid connection. At the front side of the machine, a threaded stud having a cap member attached thereto is engaged with the machine. The cap includes a sealing means, so that when the manifold is placed upon the conical outlet at the rear side of the machine, the cap can be placed on or adjacent to the opposite end of the manifold. Rotation of the cap causes the stud to force the cap into engagement with the manifold, thereby securing it in place and providing a fluid seal at each end. The manifold also includes a pin that cooperates with a plate having a slot attached to the conical outlet. Thus, by engaging the pin with the slot, proper orientation of the manifold is ensured.
While the Noren spray system enables the operator to remove the spray manifold from the forward side of the machine, it possesses several disadvantages in removing and reinstalling the manifolds. First, the construction inherently permits only single tube manifolds. While several different manifolds are typically required for different functions and stations within the machine, adequate spray coverage will frequently require multiple conduits to form a single spray system. (See for example the Hadden patent noted above.) These multiple conduits are typically interconnected to form a single manifold, so that the number of connect/disconnect operations that must be performed is kept relatively low. Unfortunately, multi-conduit manifolds are not practical with the Noren structure.
In addition, removal and installation of the manifold of Noren requires rotation of the cap to release or secure the manifold. Since the interior of the wash chamber will typically be wet, as well as the operator's hand, adequate gripping of the cap to enable its release or tightening may be quite difficult.
What is needed, therefore, is a spray manifold structure that enables easy removal and reinstallation within a commercial conveyor-type dishwashing machine so that the manifolds can be easily cleaned. Such a construction should enable relatively large manifolds to be manipulated, and should permit removal and installation from the forward side of the machine. At the same time, however, such a structure should not render the manifolds and/or the securing and sealing apparatus unduly complex.